<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Navigation bar</title>
    <style>
        #div1{border: 1px solid black;}
        ul,li{
            margin: 0;
            padding: 0;
            font-family: "黑体";
            font-size: 20px;
            list-style: none;
        }
        #div1 ul li{
            border: 1px solid blueviolet;
            width: 400px;
            float: left;
            line-height: 50px;
            height: 50px;
        }
    </style>
</head>
<body>
<div id="div1">
    <ul>
        <li><a href="#">aaa</a>
        <li><a href="#">bbb</a>
        <li><a href="#">ccc</a>
    </ul>
</div>
</body>
</html>